Status: Just an idea
The digital supervisor for a high current spark generator used for ignition fuel in the combustion chamber of a potato cannon. The main spark circuitry is based on a camera flash circuit. A FET H-bridge provides low voltage AC across a current transformer which steps 9V up to 300V. A big camera flash Cap is charged, as is a smaller Cap for the trigger. Once charged, a separate trigger fires a triac, releasing the trigger current through another current transformer to get 1.5kV, enough to ionize the air between the spark gap. Once ionized, the large 300V cap discharges across the spark gap, creating a high-current arc, enough to efficiently ignite a chamber of fuel (Tesco's value brand hair spray - which is basically a light butane/propane mix with some glue disolved in it).
Will be adding a countdown timer with 2 button up/down control, and an external dual 7-seg LED block with some shift registers to show the countdown.